1. Field of the Invention
This application relates to the field of inks and more particularly to the field of inks for ink jet printers.
2. Description of Related Art
Ink jet printing is a form of printing where very fine stable liquid droplets are discharged from an orifice and deposited onto a substrate. Use of three or more colored inks enables the user to produce full color images, text, or graphics. The ink jet printing industry is growing in parallel with the explosive development of other computer technology. Ink jet printers provide low cost, low maintenance, high speed, and high color printing quality for a wide variety of applications, from industrial labeling to office printing. However, although ink jet printing is used in more and more applications, problems with fading of the printed image when exposed to light continue plague the technology.
The printed colorants used in many ink jet inks fade when exposed to electromagnetic radiation in range of 290 nm to 1200 nm, a range present in sunlight and artificial light. This fading degrades image quality, and in many applications, such color fading is unacceptable. Accordingly, for an ink jet printer to be useful for a range of printing applications, ink jet inks and media are needed that are less susceptible to fading.
Ink colorants undergo photodecomposition via a number of oxidation and reduction mechanisms including but not limited to: electron ejection from the colorant, reaction with ground state or excited singlet state oxygen, and electron or hydrogen abstraction to form radical intermediates. While direct bond cleavage can occur, the spectral energies involved suggest that this is not a primary mechanism of photolysis of the colorants.
Which of the aforementioned mechanisms contribute to a colorant""s photodecomposition depends on many factors. First, the chemical properties of the chosen colorant are critical to its lightfastness. Generally, a more chemically stable colorant fades less upon exposure to sunlight or artificial light. Most colorants are believed to be extremely resistant to photolysis in vacuo. This belief emphasizes the relationship of the chemical environment of the printed colorant to its lightfastness.
The substrate on which the printed ink is deposited is a part of the colorant""s chemical environment, and thus can have a significant effect on lightfastness of the print. For example, cotton, rayon, and polyesters, commonly used in paper and other substrates, contain carbonyl groups. Carbonyl groups absorb light of wavelengths greater than 300 nm, such as are present in sunlight. The excitation of carbonyl groups can lead to reactive species capable of causing colorant fading. The physical characteristics of the substrate can also affect the printed colorant""s environment. The nature of the substrate may determine, in part, how much of the colorant is held on the surface. The porosity of the substrate can also affect the penetration of moisture and gases into the colorant.
The components of the ink can also have an effect on the colorant""s chemical environment, and can thus play a role in the lightfastness of the final print. The ink""s humectants, pH buffers, biocides, other additives, and even colorless photodecomposed products can catalyze the photodecomposition of the printed colorant. Likewise, the components of other inks, including the colorant(s), that mix with the ink on the substrate can contribute to the fading of the print. A notable example of catalytic fading is found in phthalocyanine dyes that catalyze the fading of certain magenta dyes. For this reason, printed blacks made by combining cyan, magenta, and yellow inks tend to fade to green, and printed blues made with cyan and magenta tend to fade to cyan.
Other various environmental factors can also affect the fading rates of printed colors. These include but are not limited to temperature, humidity, and pollutants/gaseous reactants such as O2, S2, and NO2. Also of great importance to fading rate is the spectral distribution of the radiation incident on the printed colorant.
All of the factors that affect colorant fading are interdependent to varying degrees, so it is difficult to develop an ink suitable for all general substrates or a substrate suitable for all general ink jet inks. One mechanism that has been shown to provide general protection against most mechanisms of photodegradation is aggregation of the colorant molecules. The aggregation of colorant molecules tends to reduce catalytic fading by reducing the surface area of the colorant per unit of mass that is subject to oxygen and light exposure. This point is clearly demonstrated with pigmented colorants. However, pigmented colorants tend to clog the small orifices used in ink jet printers.
Accordingly, there is a need to identify light-stable dyes suitable for ink jet printing that can be used independently or in combination and be resistant to color fading under typical environmental conditions.
The present invention provides a set of aqueous ink jet inks with improved lightfastness.
It is an object of the invention to provide an ink jet ink set with improved lightfastness suitable for thermal, piezo, or continuous ink jet printing which comprises an aqueous vehicle, a colorant, a light stabilizer to protect the colorant in the ink during exposure to light, and optionally a humectant and/or a biocide.
It is an object of the present invention to provide a combination of an ink jet ink with improved lightfastness and a substrate that reinforces the lightfastness of the ink jet ink.
It is an object of the invention to provide a combination of an ink jet ink with a printing medium that is substantially carbonyl-free.
It is an object of the invention to provide an ink jet ink set substantially stable to light or UV radiation.
Thus, in one aspect, the systems and methods described herein relate to an ink suitable for ink jet printing, comprising an aqueous vehicle, a dye having an excitation energy, and a stabilizer capable of absorbing energy of wavelengths similar to the excitation energy of the dye. In certain embodiments, the dye is substantially lightfast. In certain embodiments, the dye is a phthalocyanine dye. In certain embodiments, the dye is an azo dye. In certain embodiments, the ink includes two magenta dyes, of which one dye includes a copper complex.
In certain embodiments, the ink further includes a biocide, whereby the dye is substantially lightfast in the presence of the biocide. The biocide may be selected from 1,2-benzisothiazolin-3-one, 2-methyl-4,5-trimethylene-4-isothiazolin-3-one, 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane, and 6-acetoxy-2,4-dimethyl-1,3-dioxane.
In certain embodiments, the ink further includes a humectant, whereby fading of the dye is not promoted in the presence of the humectant. The humectant may be selected from glycerin, propylene glycol, ethylene glycol, 1,5-pentanediol, di(ethylene glycol), poly(ethylene glycol)-200, poly(propylene glycol)-425, di(propylene glycol), propylene glycol, triethylene glycol, poly(ethylene glycol)-300, 2-pyrrolidone, thiodiglycol, dimethyl imidazolidinone, glycerin, acetamide, urea, N-methyl urea, N-allyl urea, ethoxylated glycerin, sorbitol, ethoxylated glucose, dimethoxyethane, diethoxyethane, ethyleneglycol diacetate, and glycinamide hydrochloride. In certain embodiments, the dye is a yellow dye and the ink is substantially free of N-methylpyrrolidone.
In certain embodiments, the ink further includes a surfactant, and wherein the dye is substantially lightfast in the presence of the surfactant. The surfactant may be selected from non-ionic surfactants, sodium decyl diphenyl oxide disulfonate, alkyloxypolyethyleneoxyethanol, and polyoxypropylene methyl diethyl ammonium chloride.
In certain embodiments, the ink includes a yellow dye and at least one light stabilizer selected from 2,2xe2x80x2-dihydroxy-4,4xe2x80x2-dimenthoxybenzophenone-5,5xe2x80x2-bis(sodium sulfonate), 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid, histidine, and cupric sulfate. The yellow dye may include Reactive Yellow 37, Direct Yellow 107, Acid Yellow 17, Direct Yellow 86, or Direct Yellow 132.
In certain embodiments, the ink includes a magenta dye and at least one light stabilizer selected from a 4-bis(polyethoxy)aminoacidpolyethoxyethyl ester, 2,2xe2x80x2-dihydroxy-4,4xe2x80x2-dimenthoxybenzophenone-5,5xe2x80x2-bis(sodium sulfonate), 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid, 2-phenylbenzimidazole-5-sulfonic acid, histidine, and cupric sulfate. The magenta dye may include Direct Red 75, Reactive Red 23, Reactive Red 180, Direct Red 212, Acid Red 52, Acid Red 37, or Acid Red 289.
In certain embodiments, the ink includes a cyan dye and at least one light stabilizer selected from 2-phenylbenzimidazole-5-sulfonic acid, 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid, 4-bis(polyethoxy)aminoacidpolyethoxyethyl ester, and 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid. The cyan dye may include Direct Blue 199 or Direct Blue 86.
In another aspect, the invention provides a method for printing by preparing an ink jet printer with an ink as described above, disposing a sheet of substantially carbonyl-free paper in the printer, and depositing the ink on the paper.
In another aspect, the invention relates to an ink jet printer comprising an ink as described above. The printer may further include paper that is substantially free of carbonyls.
In yet another aspect, the invention relates to an ink jet printer cartridge comprising an ink as described above.
In still another embodiment, the invention provides an ink set suitable for ink jet printing, comprising a cyan ink including a substantially lightfast cyan dye, a magenta ink including a substantially lightfast magenta dye, and a yellow ink including a substantially lightfast yellow dye. In certain embodiments, the cyan dye is a phthalocyanine dye. In certain embodiments, the magenta dye includes an azo dye. In certain embodiments, the magenta ink includes two magenta dyes. In certain embodiments, at least one magenta dye includes a copper complex. In certain embodiments, the ink set further includes a black ink including a substantially lightfast black dye, such as Direct Black 19. In certain embodiments, each dye is substantially lightfast in the presence of one or more of the other dyes in the ink set.
In certain embodiments, at least one ink further includes a biocide as described above, selected such that the dye in the at least one ink is substantially lightfast in the presence of the biocide. In certain embodiments, at least one ink further includes a humectant as described above, selected such that the dye in the at least one ink is substantially lightfast in the presence of the humectant. In certain embodiments, the ink set is substantially free of N-methylpyrrolidone. In certain embodiments, at least one ink further includes a surfactant as described above, selected such that the dye in the at least one ink is substantially lightfast in the presence of the surfactant. In certain embodiments, at least one ink further includes an ultraviolet absorber, selected such that the ultraviolet absorber is capable of absorbing energy at a wavelength similar to the excitation energy of the dye in the at least one ink.
In one aspect, the invention relates to ink jet cartridge comprising an ink set as described above. In another aspect, the invention relates to an ink jet printer loaded with an ink set as described above. In certain embodiments, the printer may further be loaded with paper substantially free of carbonyls.
In yet another aspect, the systems and methods described herein relate to a method for printing by preparing an ink jet printer with an ink set as described above, loading a sheet of substantially carbonyl-free paper into the printer, and disposing ink from the ink set on the paper.
In yet a further aspect, the invention relates to a residue disposed on a surface, the residue comprising a dye having an excitation energy, and a stabilizer capable of absorbing energy of wavelengths similar to the excitation energy of the dye. In certain embodiments,the surface is paper, e.g., paper substantially free of carbonyls. In certain embodiments, the dye is substantially lightfast in the presence of the other components of the residue.
In certain embodiments, the dye is a phthalocyanine dye. In certain embodiments, the dye includes an azo dye. In certain embodiments, the residue includes two magenta dyes, of which one dye includes a copper complex.
In certain embodiments, the residue further includes a biocide as described above, whereby the dye is substantially lightfast in the presence of the biocide. In certain embodiments, the residue further includes a humectant as described above, whereby the dye is substantially lightfast in the presence of the humectant. In certain embodiments, the dye is a yellow dye and the residue is substantially free of N-methylpyrrolidone. In certain embodiments, the residue further includes a surfactant as described above, whereby the dye is substantially lightfast in the presence of the surfactant.
In certain embodiments, the residue further includes a second dye. In certain embodiments, each dye is substantially lightfast in the presence of the other dye.
In certain inks described herein, the ink includes 0.2-10.0 weight % of magenta dye, including one or more of Direct Red 75, Reactive Red 23, Reactive Red 180, Direct Red 212, Acid Red 52, Acid Red 37, Acid Red 289, or a water soluble cupric phthalocyanine dye.
In certain inks described herein, the ink includes 0.2-15.0 weight % yellow dye, including one or more of Direct Yellow 107, Reactive Yellow 37, Direct Yellow 132, and Direct Yellow 86.
In certain inks described herein, the ink includes 0.2-10.0 weight % cyan dye, including one or more of Direct Blue 199 and Direct Blue 86.
In yet another embodiment, the systems and methods described herein provide an ink set suitable for ink jet printing, comprising a cyan ink including substantially lightfast cyan dye and a stabilizer capable of absorbing energy of wavelengths similar to the excitation energy of the cyan dye, a magenta ink including a substantially lightfast magenta dye and a stabilizer capable of absorbing energy of wavelengths similar to the excitation energy of the magenta dye, and a yellow ink including a substantially lightfast yellow dye and a stabilizer capable of absorbing energy of wavelengths similar to the excitation energy of the yellow dye. In certain embodiments, each ink is an aqueous ink.
The description below pertains to several possible embodiments of the invention. It is understood that many variations of the systems and methods described herein may be envisioned by one skilled in the art, and such variations and improvements are intended to fall within the scope of the invention. Accordingly, the invention is not to be limited in any way by the following disclosure of certain illustrative embodiments.
The inks and ink sets disclosed herein employ one or more techniques for improving the lightfastness of the inks, either singly or used in combination. An ink for ink jet printing may comprise an aqueous vehicle, a substantially lightfast colorant, and a light stabilizer to protect the colorant in the ink during exposure to electromagnetic radiation in the range from 290 nm through 1200 nm. In preferred embodiments, the light stabilizer is selected to absorb radiation, especially UV radiation, approximately at a wavelength that promotes fading of the colorant.
More than one color of ink is needed to produce images of more than one color. An ink set, as the term is used herein, is a set of three or more inks of different colors which can be used in combination to produce a spectrum of printed colors. An ink set may comprise, for example, magenta, cyan, and yellow inks, optionally further including a black ink. Combinations of these dyes can produce a full spectrum of colors. Printed colors are typically made by the applying different amounts of each of the colored inks on the printing medium. As is known to those of skill in the art, the same colorant may be used in a plurality of inks at different concentrations to achieve smoother tonal transitions.
Since chromatic color is not required for black colorants, there are many lightfast dyes currently available. Because of this, metallized dyes may be used, as well as larger aggregated polyazo dyes such as Color Index (referred to as C.I. hereinafter) Direct Black 19. For cyan colorants, it is well known by those of skill in the art that phthalocyanine dyes have generally good stability under a variety of conditions. For a yellow colorant, a wide variety of yellow dyes that exhibit adequate lightfastness may be used, including some dyes currently used in conventional ink jet ink formulations. It is generally understood by those of skill in the art that conventional magenta dyes are less stable under adverse light conditions than are cyan and yellow dyes. The relative instability of magenta and black dyes underlay a longstanding preference for pigment-based inks for use in many applications, including ink jet printing inks, even though such dyes may clog the printing nozzles. In colorants, the chromophore and the auxiliary group of the dye both have a significant effect on lightfastness. Magenta dyes in the class of azo dyes tend to have superior lightfastness.
In an embodiment of the invention, the black dye is a purified form of a water-soluble metalized dye or a large aggregated polyazo dye, such as C.I. Direct Black 19. A black ink may have a dye concentration ranging from 0.1 to 25.0 percent by weight, preferably from 0.2 to 15.0 percent, and more preferably 0.2 to 12.0 percent. In an embodiment of the invention, the cyan dye is a purified form of a water-soluble, metalized phthalocyanine with the associated metal being copper, nickel, or cobalt, with the preferred cyan dye being a sulfonated copper phthalocyanine, and more preferred being a purified form of C.I. Direct Blue 86 or C.I. Direct Blue 199 or a combination thereof. A cyan ink may have a dye concentration ranging from 0.1 to 20.0 percent by weight, preferably from 0.2 to 10.0 percent, and more preferably 0.2 to 6.0 percent. In an embodiment of the invention the yellow dye is a purified form of a water-soluble azo dye, preferably C.I. Acid Yellow 17, C.I. Direct Yellow 132, C.I. Direct Yellow 107, C.I. Direct Yellow 86, C.I. Reactive Yellow 37, or combinations of these dyes or their analogs. A yellow ink may have a dye concentration ranging from 0.1 to 30.0 percent by weight, preferably from 0.2 to 15.0 percent, and more preferably from 0.2 to 8.0 percent. In an embodiment of the invention, the magenta dye is a purified form of a water-soluble azo dye the fading of which is not substantially accelerated by a cyan dye in the ink set, such as C.I. Direct Red 75, C.I. Reactive Red 23, C.I. Acid Red 37, C.I. Reactive Red 180, C.I. Direct Red 212, or combinations of these dyes or their analogs. A magenta ink may have a dye concentration ranging from 0.1 to 15.0 percent by weight, preferably from 0.2 to 10.0 percent, and more preferably from 0.2 to 8.0 percent.
The addition of some surfactants can diminish the lightfastness of the formulated ink because of the existence of light-sensitive chemical groups in the surfactant structure. Surfactants, as the term is used herein, include compounds having a hydrophilic (e.g., polar or ionic) moiety and a hydrophobic (e.g., non-polar or lipophilic) moiety, such as alkyl sulfates or phosphates, alkylammonium salts, etc. Accordingly, in an embodiment of the invention, a surfactant that does not absorb and/or is inert to radiation from 290 nm to 1200 nm is included to improve the print quality of the ink.
The aqueous ink formulations described herein may also include a suitable organic solvent, e.g., a solvent miscible with water. Suitable solvent types include ethers, such as THF, glyme, diglyme, and polyethers, alcohols, such as methanol, ethanol, propanol, isopropanol, ethylene glycol, propylene glycol, di(propylene glycol), poly(propylene glycol)-425, di(ethylene glycol), tri(ethylene glycol), poly(ethylene glycol)-200, poly(ethylene glycol)-300, pentaerythritol, ethoxylate (3/4 EO/OH), 1,5-pentanediol, glycerin, etc., and other water-miscible organic solvents, such as dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, etc. Glycerol is a preferred cosolvent. Preferably, such cosolvents, which may act as humectants in the present formulations, do not contribute to fading of or otherwise react with the dyes used in the inks or ink sets dyes. However, such concerns may be diminished by selecting a volatile solvent that substantially evaporates from the ink after printing.
A biocide may also be included in an ink formulation. A biocide is any compound which inhibits the growth of microbes or other life forms, such as yeast, bacteria, algae, or fungus, in the ink. Preferably, a biocide which does not react with or otherwise to the fading of a dye in the ink or ink set may be selected for this purpose.
Preferably, a substrate for printing, such as paper, is selected to be substantially free of carbonyls in order to reduce the contribution of the substrate to fading of the inks disposed on the surface. Various papers having this characteristic are available from common sources as described in greater detail below.
In an embodiment of the invention, the cyan ink component comprised the following elements: cyan dye, a humectant, such as glycerin, an ultraviolet absorber, such as givsorb UV, a biocide, such as 1,2-benzisothiazolin-3-one, and water. In an embodiment, the cyan ink comprised the following elements in the following amounts: Direct Blue 199, 0.5 to 10 parts, preferably 1.5-5.0 parts, and more preferably 2.0-3.0 parts; glycerin, 2.0-15.0 parts, preferably 5.0-12.0 parts; Eusolex 232 (2-Phenylbenzimidazole-5-Sulfonic acid), 0.1 to 5.0 parts, preferably 0.2 to 2.0 parts; 1,2-benzisothiazolin-3-one, 0.1 to 1.0 parts, preferably 0.1 to 0.5 parts; and parts, preferably 70 to 90 parts.
In an embodiment of the invention, the magenta ink component comprises the following elements: magenta dye; a humectant, such as glycerine; an antioxidant, such as monohydrate hypophosphite sodium salt; a biocide, such as 1,2-benzisothiazolin-3-one; an ultraviolet light stabilizer, such as 2,2xe2x80x2-dihydroxy-4,4xe2x80x2-dimethoxybenzophenone-5,5xe2x80x2-bis(sodium sulfonate) sold commercially by BASF as 4-bis(polyethoxy)aminoacidpolyethoxy ethyl ester); and water. In an embodiment, these components were the following in the following ratios: Direct Red 75, 2.0 to 12.0 parts, preferably 3.0 to 9.0 parts; glycerin, 2.0 to 15.0 parts, preferably 5.0 to 12.0 parts; monohydrate hypophosphite sodium salt, 0.01 to 1.0 parts, preferably 0.05 to 0.5 parts; 1,2-benzisothiazolin-3-one, 0.1 to 1.0 parts, preferably 0.1 to 0.5 parts; 4-bis(polyethoxy)aminoacidpolyethoxy ethyl ester), 0.1 to 5.0 parts, preferably 0.2 to 2.0parts; and water, 50 to 90 parts, preferably 70 to 90 parts.
In an embodiment of the invention, the yellow ink component comprises yellow dye, a humectant, a light stabilizer, a biocide, and water. In embodiment of the invention, these components are the following in the following ratios: Direct Yellow 132, 10.0 to 50.0 parts, preferably 15.0 to 40.0 parts; glycerin, 2.0 to 15.0 parts, preferably 5.0 to 12.0 parts; 2,2xe2x80x2-dihydroxy-4,4xe2x80x2-dimethoxybenzophenone-5,5xe2x80x2-bis(sodium sulfonate)), 0.1 to 5.0 parts, preferably 0.2 to 2.0 parts; 1,2-benzisothiazolin-3-one, 0.1 to 1.0 parts, preferably 0.1 to 0.5 parts; and water, 30 to 90 parts, preferably 40 to 80 parts.
In an embodiment of the invention, the black ink component comprises black dye, a humectant, a biocide, and water. In an embodiment of the invention, the following components are present in the following ratios: Direct Black 19, 5.0 to 40.0 parts, preferably 15.0 to 30.0 parts; glycerin, 8.0 parts; 1,2-benzisothiazolin-3-one, 0.1 to 1.0 parts, preferably 0.1 to 0.5 parts; and water, 30 to 90 parts, preferably 50 to 80 parts.
The systems and methods disclosed herein also include ink jet printers containing a lightfast ink or lightfast ink set. In certain embodiments, such printers may further be loaded with paper substantially free of carbonyls. The systems and methods disclosed herein also include ink jet printer cartridges, such as replacement ink cartridges, containing one or more lightfast inks as described herein. The systems and methods disclosed herein relate further to paper, including paper substantially free of carbonyls, printed with one or more inks of the present invention, e.g., bearing a residue left from the evaporation of solvent or other volatile compounds from one or more lightfast inks as described herein.